Triose kinase liver

In the liver, kidney, and intestine, fructose can be converted to glycolytic/ gluconeogenic intermediates by the actions of three enzymes—fructokinase, aldolase B, and triokinase (also called triose kinase)—as shovra in Figure 24-1. In these tissues, fructose is rapidly phosphorylated to fructose 1-phosphate (FIP) by fructokinase at the expense of a molecule of adenosine triphosphate (ATP). This has the effect of trapping fructose inside the cell. A deficiency in this enzyme leads to the rare but benign condition known as essential fmcto-suria. In other tissues such as muscle, adipose, and red blood cells, hexokinase can phosphorylate fructose to the glycolytic intermediate fmctose 6-phosphate (F6P). 

Liver metabolizes up to 85% of orally administered D-fructose. Fructokinase, aldolase, and triose kinase are important control enzymes for hepatic D-fructose metabolism.62 The activities of these enzymes are subject to dietary composition and hormonal control. Total fructokinase, aldolase, and triose kinase decrease to about half or less of their normal activity on fasting for 48 to 72 hours, and are restored to normal in 24 hours upon D-fructose administration. Longterm feeding of D-fructose results in the maintenance of a considerably higher level of all three enzymes, an effect also seen with rats maintained on a high-fat or high-protein diet.62... 

The fate of dihydroxyacetone phosphate is also varied—it may be transformed to a-glycerophosphate, or through the reaction catalyzed by the triose isomerase, it may yield D-glyceraldehyde-3-phosphate, which in the presence of triose phosphate dehydrogenase and phosphoglycerate kinase yields 3-phosphoglycerate. This degradation pathway is complete only in liver, and it is not known to what extent it operates in muscle. 

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